The invention relates to improvements in apparatus for damping vibrations, especially between the output element of an engine (such as the internal combustion engine of a motor vehicle) and a power train (particularly the power train including the change-speed transmission in a motor vehicle). More particularly, the invention relates to improvements in torsional vibration damping apparatus of the type wherein at least two flywheels are rotatable relative to each other against the opposition of damper means, wherein one of the flywheels is connectable to the output element of the engine, and wherein another flywheel is connectable with the input element of a change-speed transmission, especially by way of a clutch (such as a friction clutch).
Vibration damping apparatus of the above outlined character normally employ one or more dampers which comprise elastic energy storing elements (such as circumferentially extending coil springs) installed or operating between the flywheels in such a way that they oppose rotation of the flywheels relative to each other and undergo compression and store energy when one of the flywheels is caused to change its angular position with reference to the other flywheel, and/or energy storing elements which act in the axial direction and employ or cooperate with friction pads or linings to generate friction (i.e., hysteresis). As a rule, or in many instances, the energy storing elements which act in the axial direction of the flywheels are connected in parallel with the damper or dampers acting in the circumferential direction of the flywheels.
It has been found that, though the just described conventional vibration damping apparatus are quite satisfactory under certain operating conditions (i.e., they can damp certain types of vibrations and they can also reduce noise which develops in response to angular movements of the flywheels relative to each other), the operation of all presently known apparatus constitutes a compromise between an optimum operation under first circumstances and a less satisfactory operation under different second circumstances. For example, purely mechanical vibration damping apparatus cannot satisfactorily oppose a full spectrum of vibrations which are likely to develop at different rotational speeds of the engine and/or under different loads and/or on different types of terrain and/or in different types of motor vehicles. The same applies for the reduction of noise under such widely different circumstances. The bulk and cost of mechanical vibration damping apparatus increase considerably if such apparatus are to be designed with a view to satisfactorily oppose vibrations and to reduce noise under two or more different circumstances which require different modes of vibration damping and/or different modes of noise reduction. Another drawback of purely mechanical vibration damping apparatus is that they cannot conform their damping characteristics to a variety of widely different operating conditions which vary within wide ranges (for example, to different operating conditions which arise as a result of acceleration of the engine-driven flywheel from a relatively low speed to a much higher speed or vice versa). One of the reasons for such lack of versatility of mechanical vibration damping apparatus is that the histeresis of their energy storing elements which act in the circumferential direction of the flywheels cannot adequately conform to changing operating conditions. Moreover, mechanical vibration damping apparatus are prone to malfunction and their parts are subject to extensive wear.
Another drawback of presently known vibration damping apparatus is that they do not allow for extensive angular movements of the flywheels relative to each other. In other words, the damping action of the damper or dampers must be very pronounced, at least during the major part of the extent of angular displacement of the flywheels relative to each other. This prevents the conventional apparatus from effectively damping large-amplitude vibrations.
An object of the invention is to provide a novel and improved vibration damping apparatus which can be used as a superior substitute for heretofore known apparatus between the engines and the power trains of motor vehicles.
Another object of the invention is to provide an apparatus which can effectively filter vibrations between the engine and the change-speed transmission of a motor vehicle under a wide range of operating conditions.
A further object of the invention is to provide an apparatus which is effective at low, medium and high rotational speeds of its flywheels as well as at resonance RPM and during starting and stoppage of the engine.
An additional object of the invention is to provide an apparatus whose damping characteristics (i.e., its ability to dissipate energy) can readily conform to different vibration generating and/or noise generating parameters of the vehicle.
Still another object of the invention is to provide a relatively simple, compact and inexpensive apparatus which can oppose vibratory movements and the generation of noise in a number of different ways (including hydraulically and mechanically) and at least as effectively as specially designed inflexible (low-versatility) conventional vibration damping apparatus.
A further object of the invention is to provide an apparatus whose parts can be mass-produced in available machines and with a minimum of material removing treatment.
Another object of the invention is to provide an apparatus whose useful life is long and wherein the parts are subject to less wear than in conventional apparatus.
An additional object of the invention is to provide the apparatus with novel and improved flywheels.
Another object of the invention is to provide a novel and improved method of assembling the above outlined apparatus and a novel and improved method of coordinating the action of two or more hydraulic and/or mechanical dampers.
A further object of the invention is to provide the apparatus with novel and improved damper means and to provide the apparatus with novel and improved means for confining and shielding the damper means.
Another object of the invention is to provide a motor vehicle which embodies the above outlined apparatus and to provide a novel and improved torque-transmitting connection between the engine and the change-speed transmission of a motor vehicle.
An additional object of the invention is to provide a novel and improved torque-transmitting connection between the relatively movable parts of the above outlined apparatus.
The invention is embodied in an apparatus which can be used to damp vibrations, particularly torsional vibrations between an engine (such as the internal combustion engine of a motor vehicle) and a power train (particularly a power train including a change-speed transmission and a friction clutch which can establish a torque-transmitting connection between the input element of the transmission and the output element of the engine), wherein a first flywheel is connectable with the engine, wherein a second flywheel is rotatable relative to the first flywheel and is connectable with the power train (particularly by way of a clutch, such as the aforementioned friction clutch), and wherein a damper means operates between and yieldably opposes rotation of the first and second flywheels relative to each other. More particularly, the invention resides in improvements in the above outlined apparatus, the improvements including at least three of the following features:
(a) One of the flywheels includes sections which define an annular compartment for a supply of viscous fluid medium (preferably a lubricant of pasty consistency) which at least partially fills the compartment, the compartment has an at least substantially closed cross-sectional outline and the damper means comprises at least two energy storing elements (such as springs, especially coil springs) which are disposed in the annular compartment at the same distance from the axis of the one flywheel and are directly or indirectly engageable or engaged by the sections of the one flywheel;
(b) a flange (e.g., a flat metallic disc) extends radially into the compartment and engages the energy storing elements and at least substantially seals the compartment, and means (such as a coupling including a portion of the flange) is provided to transmit torque between the flange and the other of the first and second flywheels;
(c) the flywheels are rotatable relative to each other against the opposition of the energy storing elements through angles of at least 25 degrees in clockwise and counterclockwise directions starting from a neutral position which may but need not always be the same;
(d) the total number of energy storing elements is less than five and such elements jointly extend along an arc which approximates between 70 and 96% of a complete circle;
(e) the energy storing elements jointly extend along an arc of 70-96% of the circumferential of the one flywheel; and
(f) the energy storing elements are prefabricated or pre-curved to exhibit a curvature with a radius of curvature which equals or approximates the radius of the annular compartment (this simplifies the assembly of the damper means with the sections of the one flywheel).
The flange is preferably provided with substantially radial outwardly extending arms which project into the compartment and engage the energy storing elements. The flange can be further provided with one or more ribs which extend in the circumferential direction of the one flywheel and merge into the arms. The sections preferably further define an annular passage which communicates with the annular compartment and receives the ribs of the flange.
The sections of the one flywheel preferably include two substantially shell-shaped sections at least one of which can consist of sheet metal. Alternatively, at least one of the sections can constitute a metallic casting.
The sections are provided with integral or separately produced inserts which constitute abutments for the energy storing elements and extend into the compartment. The latter preferably extends along an arc of 360xc2x0, i.e., it can constitute a circumferentially complete annular compartment. The abutments can include or constitute rivets which are secured to the sections of the one flywheel, and such abutments are or can be disposed at opposite sides of the arms of the flange in the neutral positions of the flywheels. The inserts can constitute integral pocket-like portions of the sections of the one flywheel.
The abutments flank the arms of the flange and at least one arm of the flange can be shorter or longer than the adjacent abutments (as seen in the circumferential direction of the one flywheel). Each energy storing element of the damper means is located between an arm of the flange and a pair of abutments, and the damper means can further comprise retainer means (e.g., cup-shaped spring retainers) between at least one of the arms and the respective energy storing element. The arrangement is preferably such that each retainer means at least substantially fills the respective portion of the annular compartment so that each such retainer means can act not unlike a piston or plunger to displace the fluid medium in the compartment in response to angular displacement of the flange and the one flywheel relative to each other. Such piston or pistons can be provided with one or more peripheral recesses or notches and/or one or more holes for the passage of fluid medium therethrough (the fluid-displacing action of such notched, recessed or hollow piston or pistons is less satisfactory than that of a piston which is devoid of holes, notches and/or recesses and has a peripheral surface in immediate or close proximity to the surfaces bounding the adjacent portion or portions of the annular compartment).
The compartment can have a substantially constant cross-sectional area all the way from one of its ends to the other end (if it is not a circumferentially complete compartment) or in each and every portion thereof (if it constitutes an endless annular compartment). Alternatively, the compartment can have at least one first portion with a first cross-sectional area and at least one second portion with a different second cross-sectional area. The second cross-sectional area can exceed the first cross-sectional area and can be adjacent one end portion of one of the energy storing elements (e.g., in the form of arcuate coil springs) in the neutral positions of the first and second flywheels.
The damper means can include a first damper which comprises the aforementioned energy storing elements in the annular compartment, and at least one second damper which is preferably disposed radially inwardly of the first damper and can include additional energy storing elements. The flange is preferably provided with recesses for the energy storing elements in the compartment and with arcuate windows for the additional energy storing elements. The aforementioned arms alternate with the recesses and the flange is further provided with substantially radially extending webs which alternate with the windows and engage the additional energy storing elements. At least one spring retainer (such as the aforementioned cupped piston-like retainers) can be provided between at least one arm and the adjacent energy storing element in the annular compartment and/or between at least one of the webs and the adjacent additional energy storing element. The retainer or retainers can be provided with sockets and the adjacent arms or webs of the flange can be provided with projections (e.g., in the form of lobes) which extend into the sockets of the adjacent retainers in the circumferential direction of the one flywheel. Such projection(s) of the arm(s) or web(s) serves or serve to maintain the respective energy storing element(s) out of contact with the sections of the one flywheel or out of contact with the flange radially outwardly of the respective energy storing element or elements.
The second damper can be connected in parallel with the first damper, e.g., by way of the aforementioned flange. Alternatively, the first and second dampers can operate in series.
The energy storing elements of the damper means can form several groups (the energy storing elements of the first damper can form at least one group and the energy storing elements of the second damper can form one or more groups), and the flange and the sections of the one flywheel include means (such as the aforementioned abutments of or on the sections and the aforementioned arms and webs of the flange) for engaging at least two groups of energy storing elements during different stages of angular movement of the first and second flywheels relative to each other. The arrangement may be such that one group of energy storing elements of the second damper begins to store energy in immediate response to angular displacement of at least one flywheel from the neutral position, that another group of energy storing elements of the second damper begins to store energy after at least one of the flywheels completes a certain angular movement from the neutral position, and that the energy storing elements of the first damper begin to store energy simultaneously with the one or the other group or in response to a different angular displacement of at least one of the first and second flywheels from neutral position.
If the damper means includes two dampers, the windows for the energy storing elements of the second damper can be distributed in the flange in such a way that each window is located radially inwardly of a different recess for an energy storing element of the first damper. The length of each window (as seen in the circumferential direction of the one flywheel) can equal or approximate the length of a recess. The number of energy storing elements in the first and/or second damper need not exceed four.
Those sections of the one flywheel which define the annular compartment preferably include portions which are disposed radially inwardly of the compartment and define a preferably circumferentially complete annular passage which communicates with the compartment and is at least substantially filled by the rib or ribs of the flange. The flange can fill the passage to such an extent that it establishes with the one or the other section an annular gap having a width of 0.1-2 mm in the axial direction of the one flywheel. The gap can be a single gap or a composite gap having a first portion at one side and a second portion at the other side of the flange.
The energy storing elements of the second damper are preferably confined in arcuate grooves which are defined by the sections forming the annular compartment, and such grooves together form a second compartment for the respective energy storing elements. The aforementioned passage is disposed between the annular compartment and the grooves and communicates with the compartment as well as with the grooves. Those surfaces of the sections which bound the grooves can closely conform to the outlines of energy storing elements of the second damper. The energy storing elements of the second damper can also constitute coil springs which are prefabricated or pre-curved so as to have a curvature (prior to installation in the one flywheel) which equals or approximates the curvature of the arcuate grooves. The additional energy storing elements (of the second damper) can abut the rib or ribs of the flange under the action of centrifugal force when the one flywheel is set in rotary motion at an RPM which suffices to subject the additional energy storing elements to the action of a centrifugal force strong enough to tend to propel the additional elements radially outwardly and against the rib or ribs of the flange. Alternatively, or in addition to abutting the rib or ribs of the flange, the additional energy storing elements can abut the surfaces which bound the grooves, at least while the flywheels rotate and the additional elements are acted upon by centrifugal force. Each groove can constitute a circumferentially complete groove and can contain abutments for the additional energy storing elements; such abutments are provided on the sections of the one flywheel and cooperate with the webs of the flange to cause the additional elements to store energy in response to angular displacement of the abutments relative to the webs and/or vice versa. Each abutment can include one or more rivets which connect it to the one flywheel. Each abutment can be provided with a substantially flat surface which is in relatively large-area contact with the end portion of the adjacent additional energy storing element.
The additional energy storing elements can be located in the windows of two substantially disc-shaped members which flank the flange and are connected to the other flywheel. The flange then comprises means for connecting the first damper in series with the second damper.
The apparatus further comprises a coupling or connection which includes a first half on the first flywheel and a second half on the other flywheel. The coupling serves to transmit torque between the two halves which are in torque transmitting engagement with each other in predetermined axial positions of the first and second flywheels relative to each other. One half of the coupling can be provided on the flange and the other half of the coupling can be provided on the other flywheel (e.g., on a disc-shaped member which is bolted, riveted or otherwise secured to the other flywheel). The annular compartment can constitute a portion of an annular chamber which is defined by the one flywheel and which further includes the aforementioned passage for the flange and the aforementioned grooves for the additional energy storing elements. Such apparatus can further comprise means for sealing the chamber from the atmosphere, and the sealing means can include a sealing member on one of the flywheels and a sealing surface provided on the other flywheel and being engaged by the sealing member when the two halves of the coupling are assembled and can transmit torque. The halves of the coupling can comprise mating tooth-like projections which are separable from each other in response to axial shifting of at least one flywheel relative to the other flywheel from a predetermined axial position in which the projections of one half mate with the projections of the other half.
The compartment or compartments are preferably provided in the first flywheel, i.e., in that flywheel which can be driven by the output element of the engine if the apparatus is installed in a motor vehicle.
The fluid medium in the aforementioned chamber of the one flywheel preferably fills the annular compartment and the passage as well as a portion at least of the second compartment (including the aforementioned annular grooves) so that the additional energy storing elements are contacted by the fluid medium.
The apparatus can further comprise at least one friction generating device which operates between the two flywheels to oppose angular movements of such flywheels relative to each other, either during each stage or during selected stages of such angular movements. In other words, the friction generating device or devices can include means for opposing one or more predetermined portions of angular movement of the first and second flywheels relative to each other. The friction generating device or devices can be installed in or externally of the aforementioned chamber. Each friction generating device can operate in series with the first and/or second damper of the damper means. For example, at least one first friction generating device can operate in parallel with the first damper so as to oppose rotation of the flywheels relative to each other with a first force, and one or more additional friction generating devices can operate in parallel with the second damper to oppose rotation of the flywheels relative to each other with a different second force, preferably a lesser force.
The mutual spacing of abutments in the annular compartment and/or in the second compartment of the aforementioned chamber can exceed the length of at least one energy storing element in the respective compartment (as considered in the circumferential direction of the one flywheel).
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.